A multidisciplinary study of 163 patients treated at the NCI for soft tissue sarcomas allowed the correlation of a number of histologic features (histologic type, mitosis, necrosis, pleomorphism, cellularity, and matrix) of the primary lesion to time to recurrence and overall survival of the patients. The results of the stratified analyses show that necrosis is the single best histopathologic parameter to predict the time to recurrence (P = 0.025) and the overall survival of the patients (P = 0.002). Necrosis in the primary lesion is also of value in predicting survival after the first recurrence has taken place (P = 0.001). The value of necrosis in the primary lesions predicting the clinical course after recurrence appears to be independent of age, sex, location, and size of the tumor. The authors propose a grading system based on histologic typing and histologic parameters to identify a group of lesions with minimal metastatic potential (Grade 1), and on the use of necrosis to distinguish between aggressive lesions with good patient survival (Grade 2) and aggressive lesions with poor patient survival (Grade 3).